Ankle-Foot Orthoses (AFOs) are braces that structurally compensate for weak or deformed ankle joints. Typically, an AFO will limit the range of motion of an ankle to prevent the foot from dropping or rotating into a position that hinders walking. Ankle braces dating back fifty years or more were commonly constructed from metal frames with leather straps. Shoes typically were characterized by prominent heels, with a heel breast that could engage a stirrup, so early ankle braces often attached to or around a heel structure.
Over the decades, shoe structures and materials have evolved considerably. Typical modern footwear has become relatively more flexible and compliant compared to footwear contemporary to earlier foot braces. With few exceptions, modern shoes no longer have a heel structure to use as a point of attachment. In addition, a focus on comfort in the construct of the sole of modern footwear has led to the use and development of resilient synthetic materials, sometimes containing foams or gels, for added cushioning. This development, although preferable for shoe comfort, poses specific challenges to cutting-edge shoe orthosis companies.